1-tg^2a+tg^4a/cos^2a

Question

1-tg^2a+tg^4a/cos^2a

Answer 1

cos2a+1)*tg²a-1= = (cos²a - sin²a + cos²a + sin²a)*sin²a/cos²a - sin²a - cos²a = = sin²a - cos²a = - cos2a

Comments

или вот еще cos2a+1)*tg²a-1= = (cos²a - sin²a + cos²a + sin²a)*sin²a/cos²a - sin²a - cos²a = = sin²a - cos²a = - cos2a